Vol 66, No 1 (2019)

Based on the approaches developed by the National Research University Moscow Power Engineering Institute (NRU MPEI) and the Energy Research Institute (ERI), the results of calculations of total world energy consumption and by groups of countries for the period up to 2050, with allowance for the anticipated climate changes, as well as resource and environmental restrictions, are presented. The estimates of energy consumption in various world regions for the period up to 2050 are based on a historical extrapolation approach to the research of energy consumption dynamics with allowance for the dependence of its optimal level on natural and geographical conditions. Using the SCANER simulation computer system developed by the Energy Research Institute for the study of energy markets, forecast fuel and energy balances for various regions have been made, which are aimed at meeting the national commitments on the Paris Agreement (2015) of the countries participating in the UN Framework Convention on Climate Change (UNFCCC), and international flows of the main energy carriers have been calculated. Estimates of the possible oil and gas export from Russia in the context of various scenarios for the development of the world energy sector have been made. It is shown that the fundamental processes currently taking place in the global energy complex, such as the development of new renewable and nonrenewable energy sources, the control and constraint on greenhouse gas emissions, and the uncertain status of nuclear energy, will contribute to an increase in demand for oil and, especially, natural gas from Russia and facilitate the rise in exports of these energy carriers, predominantly in the Asian direction.

A review and analysis are presented of the available foreign publications on the modern methods of design, manufacture, design calculation, and operation of water-cooled condensers for large steam turbines used in Russia and abroad. A list of the world’s leading manufacturers of condensers is presented. The adopted alternative arrangements of condensers concerning the turbine centerline and available condenser design styles are examined. The condensers for turbines manufactured by General Electric and the Leningrad Metal Works (LMZ) are compared by their design characteristics and performance indices. The arrangements of tube bundles used in designing and upgrading condensers in Russia and abroad are presented. Information is given on construction materials of condenser tubes and tube sheets as well as on the methods for tube-to-tube sheet attachment. Data on air removal equipment of the condensers are presented. The basic lines of evolution of steam jet ejectors, water-ring pumps, and hybrid air removal systems are considered. The methods of condenser heat-transfer surface cleaning adopted in Russia and abroad are compared. The data on the number of failures and the basic causes of these failure are presented. The procedures for replacement of tubes during repair or modernization of condensers and the symptoms used to determine the necessity of tube replacement are described. Information derived from the authors' investigations and a review of American publications on the potential for heat transfer enhancement in the condensers through the use of shaped tubes is given. The condenser design methods and standards applicable in Russia and abroad are assessed. The lines of improvement in the design of condensers for modern steam turbines of thermal and nuclear power stations are outlined.

The article presents the results from an incisive analysis of using end and internal honeycomb seals (HS) in two T-60/73-7.8/0.04 steam turbines produced by the Kaluga Turbine Works (in Russian, KTZ) intended for being used at the Ufa TETs-5 combined heat and power plant. The honeycomb seals were installed in the flow path of these turbines on the customer’s request and have been applied at KTZ for the first time. Expectedly, the use of HSs could decrease parasitic steam leaks, thereby resulting in improvement of the turbine efficiency. According to assessments made by the ARMS research and production enterprise and expectations of KTZ specialists, the replacement of conventionally designed labyrinth seals by seals with honeycomb inserts would make it possible to increase the turbine efficiency by approximately 1% due to essentially narrower radial gaps in the end, diaphragm, and shroud seals. Experimental investigations of HSs during their operation under model test bench conditions have shown that parasitic leaks of working fluid may indeed be reduced using these seals. However, this is only possible for a narrow range of optimal ratios between the physical design parameters of the seal honeycomb structure and the gap between the stator and rotor elements. The ideas of applying HSs in steam turbines were borrowed from the experience gained from operation of gas turbine engines. In steam turbines whose supports are made with plain bearings, the rotor rotates over an intricate trajectory with respect to the steam turbine casing longitudinal axis. With vibration that takes place under steam turbine real operating conditions, the use of HSs is not expedient, at least in turbines with a flexible shaft. It is shown, taking a particular example, that the narrow gaps (0.15–0.30 mm) between the steam turbine stator and rotor elements as recommended by the HS manufacturers, with which the useful effect from application of HSs manifests itself, cannot be implemented under field conditions. Such statement stems from the results of acceptance tests of two T‑60/73-7.8/0.04 steam turbines produced by KTZ that were carried out at the factory’s test bench. It has been found after opening the turbine and examining its parts after the thermal tests on the bench that all HSs made with narrow radial gaps were destructed. The commissioning team involving the customer’s representatives has recognized that further operation of the steam turbines with such seals is impossible. A decision was made at KTZ to fit the steam turbines with new seals with increased radial gaps. Had the turbines not been opened at the factory, the destructions of their HSs would have been revealed in the course of steam turbine overhaul after 6 years of their operation.

Formation of nitrogen oxides in the combustion of pyrolysis gases from oil shale thermal processing (such as semicoke and generator ones) in recirculation flue gas containing air was investigated. The parameters that can considerably affect the formation of nitrogen oxides, such as lower and upper flammability limits, the minimum content of oxygen in the air-flue gas mixture at which ignition of a combustible gas can occur, fundamental burning velocity were determined, and the adiabatic flame temperature under the stoichiometry conditions were calculated. A design of a burner intended for reliable operation when the combustion air has a high content of recirculation flue gases is examined. For this purpose, 5–10% of combustible gas is burned in pure air in the central part of the burner, while the remaining gas is burned in the peripheral part of the burner where recirculation flue gases are fed together with combustion air. The results of full-scale experiments carried out in a type TP-101 boiler at the Estonian thermal power station and a Е-135-3.2-440DG VKG Energia OÜ boiler (in Kohtla-Järve, Estonia) are presented. The effect of flue gas recirculation on the formation of nitrogen oxides during burning of semicoke gas only or a mixture of semicoke and generator gases is demonstrated. Data on the formation of nitrogen oxides in burning semicoke gas with a high excess air are presented. The effects of additional ballast matter, such as inert components of flue gases or air excess, which can be considered as an inert matter in calculation of the combustion product temperature, on nitrogen oxides formation are compared. The fact that the processes running in the flame front and the flame front temperature proper can affect nitrogen oxide formation is noted. The main result of the investigation is that quite low NO_x concentrations (as low as 40–50 mg/Nm³) can be achieved by using flue gas recirculating technique only, without staged supply of air or fuel.

Two algorithms used to correct the semi-implicit numerical scheme for time integration of the conservation equations incorporated into the KORSAR/GP computer code two-liquid model are presented. The KORSAR/GP code has been developed jointly by specialists of the Federal State Unitary Enterprise Aleksandrov Research Institute of Technology and Gidropress Experimental Design Office; in 2009, the code was certified at the Federal Service for Environmental, Technological, and Nuclear Supervision (Rostekhnadzor) as applied to numerical safety assessment of VVER-based reactor plants. In the semi-implicit scheme, the convective terms appearing in the phase momentum conservation equations are written in an explicit form. The mass and energy flows of the phases are represented implicitly with respect to phase velocities, and the transferred donor quantities are calculated based on the parameters taken from the previous time layer. Owing to linearization of unsteady and source terms, the linear system of finite difference equations is solved in a noniteration manner. The first of the presented algorithms compensates for numerical imbalances of phase masses and energies resulting from linearization of unsteady terms appearing in the discrete equations and ensures conservativeness of the scheme. The second algorithm introduces correction for the nonphysical redistribution of coolant mass and energy over the computational cells if a change occurs in the phase motion direction within a time step when the scheme of approximating the convective terms becomes “antidonor” with respect to flow. The numerical imbalances and refinements taking into account the correction of donor quantities are computed at each time step according to the proposed correlations and are used for making compensation at the next time step as supplementary sources in the conservation equations. Results from testing the correction algorithms in the KORSAR/GP code are presented. The effectiveness of the imbalance compensation algorithm is confirmed by solving a problem involving the natural circulation loop heating process. The adequacy of the “antidonor” scheme correction algorithm is demonstrated on problems involving steplike initial distribution of the scalar parameters of a stagnant single-phase gaseous or water coolant in a horizontal tube when the flowrate at the tube inlet has different signs at different time steps.

The efficiency of power units designed for different applications is determined by their power density, weight, dimensions, and reliability, and it can be increased by introducing new engineering solutions to increase heat transfer rate on heat-release surfaces in heat-transfer apparatuses (HTA). Heat transfer is often enhanced through the use of interacting swirled flows. The heat-transfer enhancement is achieved due to interaction of swirled and transit (with a pitch equal to infinity) flows along a convex heat-release surface. The efficiency is estimated of HTAs with convex and concave heat-release surfaces on which precisely this method of heat-transfer enhancement is used. An annular channel is selected as the basic HTA. This selection is due to the fact that the channel elements (i.e., the outer pipe has a concave heat-release surface, and the inner rod has a convex release surface) are components of various heat exchangers and nuclear power installations. In evaluating the efficiency of HTAs, the known correlations for heat transfer and hydraulic resistance in smooth annular channels and the relationships for heat transfer coefficient on convex and concave surfaces of annular channels with swirled and transit flows obtained by the author were used. It is demonstrated that an increase in the heat transfer is greater than a rise in the hydraulic resistance with the interaction of swirled and transit flows at heat-transfer surfaces in a certain range of flow conditions and geometries. Evaluation of the HTA’s effectiveness based on the known criteria has revealed that the heat-transfer enhancement method using interacting swirled and transit flows is comparable in terms of its effectiveness with other known methods of heat-transfer augmentation.